Liquid aspirators are commonly employed to apply diluted solutions containing chemicals such as pesticides, fungicides, herbicides, and fertilizers to lawns or garden foliage. Typically, sprayers of this type are attached to a garden hose. The pressure of the water delivered through the hose creates a negative pressure gradient that causes a chemical solution to be aspirated into the water stream, thereby providing a diluted solution to be sprayed.
In general, aspiration sprayers include a container for holding the chemical solution to be diluted and sprayed and a sprayer/mixing head. The base portion of the sprayer head serves as a cover for the chemical container. Such sprayer heads generally include an adapter for connecting the sprayer head to a standard garden hose, and a hand valve for turning on and off the flow of water from the garden hose. The sprayer head also includes an aperture over which water from the garden hose passes to mix with undiluted chemical solution from the container. Such sprayer heads may also include a venturi chamber in which the water from the garden hose mixes with the chemical from the container.
In principle, as water passes over the aperture or through the venturi chamber, a siphoning or vacuum action, is created by virtue of the velocity of the water passing over the aperture or through the chamber, to draw chemical from the container into the water stream for dilution. The basis of operation of these sprayers is Bernoulli's principle. The effect is also referred to as the Kuanda effect.
In common use today are 28 mm. aspiration sprayers used by a number of manufacturers. Until recently, such units were shipped with the sprayer/mixing head attached to the side of the container of liquid chemical in some manner. Liquid in the container is contained by a standard "child-proof" cap. Before use, the consumer removes the cap, attaches the sprayer head and connects a garden hose.
When the product container is emptied, such removable sprayer heads can be removed and attached to another container. Although economically advantageous, removable sprayer heads introduce the potential of exposure of adults and especially children to concentrated chemical product. In many instances the contained product is a potentially hazardous chemical such as an insecticide or herbicide.
Within the past few years, however, new "on-the-bottle" units have entered the market. With on-the-bottle units, the consumer merely connects the unit to a hose and is ready to spray. Because on-the-bottle units are designed to be discarded once the attached product container is emptied, such units are preferably inexpensive to manufacture.
Generally, leakage of the potentially hazardous chemical product is possible through the product aperture and through a small air vent hole, each of which are necessary elements of any aspiration type sprayer. Several manufacturers have introduced on-the-bottle units that are described as sufficiently sealed when not in use for safe shipment and storage.
U.S. Pat. No. 4,901,923, for example, discloses a variable dilution ratio hose-end aspirator sprayer. The sprayer comprises a container for housing the liquid to be mixed with the water and a mixing head having a nozzle at one end thereof and a garden hose attachment device at the other end thereof. The sprayer also includes a mixing chamber within the mixing head, a hose for communicating the liquid from the container to the mixing head and a disk having a plurality of apertures therein rotatably mounted in the mixing head to control flow from the container to the mixing chamber. A flow tube communicates liquid in the container to the inlet in the mixing chamber though a selected aperture in the disk so that the liquid is diluted with pressurized water at a dilution ratio determined by the size of the aperture aligned with the tube and the mixing chamber. The sprayer also includes a cleaning orifice positioned circumferentially from the mixing chamber so that each aperture of the disk may be selectively aligned with the cleaning orifice for cleaning.
U.S. Pat. No. 5,039,016 also discloses an aspiration-type chemical sprayer for dispensing small quantities of a liquid-based chemical into a stream of carrier fluid. The sprayer includes a sprayer head assembly sealingly mounted onto a container for storing the chemical to be disbursed. The sprayer head assembly also includes a multi-function unitary valve for providing a range of aspiration rates simultaneously with full communication of the container interior to atmospheric pressure. The valve may also include means for positive and simultaneous closure of the aspiration and vent passages so as to seal the chemical in the container when the sprayer is not in use.
U.S. Pat. No. 5,100,059 similarly discloses an aspiration-type chemical sprayer including a sprayer head assembly sealingly mounted onto a container holding chemicals such as pesticides or fertilizers. A unitary valve in the sprayer head assembly controls carrier fluid flow from a pressurized source of water while simultaneously providing a controlled aspiration rate and full communication of the container interior to atmospheric pressure. The valve additionally includes simultaneous closure of the carrier fluid, aspiration and vent passage ways so as to seal the chemical in the container when the sprayer is not being used.
U.S. Pat. No. 5,007,588 also discloses an aspiration-type sprayer comprising a sprayer head which is permanently attachable to a container in which additive material is received. The sprayer head may be moveable between positions controlling the degree of aspiration affected, and is provided with a cap moveable between a first position in which the cap seals the container and prevents the additive material from escaping therefrom and a second position in which the container is unsealed and aspiration of the contents thereof can take place. Elements may be provided as part of the sprayer assembly for controlling the flow of the aspirating fluid. The cap is secured in its sealing position by an element which require special manipulating for release, thereby providing an important safety feature.
Similarly, Green Sweep.RTM. has recently introduced a sprayer in which a water shut-off valve is linked with the product aperture seals so that one rotational movement results in both water and product being released at the same time (or simultaneously shut off).
Although it is desirable to enable on/off control of both water inflow and product flow in a single movement, this feature hinders the ability to provide a short product channel as both the aperture for water flow and the product aperture must be close enough to the control cylinder to be within the diameter of the control cylinder. The product channel of the Green Sweep sprayer, for example, traverses two right angles before opening into the carrier stream, resulting in a product channel length of over one (1) inch.
The product channel (i.e., the passage through which the chemical to be diluted passes after leaving the container to reach the product aperture and enter the carrier stream) of aspiration type sprayers is generally formed during injection molding with the use of a pin of appropriate diameter. In sprayer head designs that are shipped disconnected from the product container, the product channel is relatively short and straight, essentially passing linearly through a thin plastic base or cap member. Such product channels are typically 3/16 inch in length. The increased complexity and extension of product channel (arising from both the requirement of appropriate sealing during nonuse in the case of on-the-bottle designs and attempts at single movement control) create the potential of significant reduction in quality. Slightly bent pins used to create the product passage or small pieces of flashing can create performance failures or even non-performance at water pressure levels under 20 PSI.
Although the feature of single-movement control has complicated prior sprayers as set forth above, absence of this feature creates the need for two control valves, which complicates consumer instruction and use, increases the potential for leakage and may increase manufacturing cost.
It is therefor desirable to develop an on-the-bottle sprayer capable of single-movement control in which the length of the product channel is substantially minimized and in which the product channel is substantially linear.
It is also desirable that such a sprayer be simple in operation and inexpensive to manufacture.